1. Field of the Invention
This invention relates in general to a machine for making a thin plastic covering in the form of a tubular presized sleeve for application to a rigid base article.
2. Description of the Prior Art
The prior art discloses two basic machines for forming and applying a thin plastic covering or tubular sleeve to a rigid base article such that a subsequent heat-shrinking process results in a tightly constrictive plastic covering. U.S. Pat. No. 3,110,554 to Yazumi discloses an apparatus for labeling packages. A thin rectangular thermoplastic blank is formed into an open-ended tubular sleeve using a heat-sealing bar to form a lengthwise fusion seam. The diameter of the tubular sleeve is made only slightly larger than the diameter of the article to be covered. The sleeve is then placed directly on the body portion of the rigid article and a thermal operation contracts the heat-shrinkable plastic sleeve to make it conform tightly to the body portion surfaces of the article therebeneath.
U.S. Pat. No. 3,802,942 to Amberg et al, assigned to the same common assignee as the present application, discloses another type of sleeve-making apparatus. The thin plastic covering is supplied in the form of a large roll or web which is serially cut into uniform-size rectangular blanks. The plastic blanks are introduced to a plastic sleeve forming mechanism. The leading edge of the plastic blank is retained on a cylindrical mandrel by the pressure differential created by a vacuum applied through a series of vacuum ports formed in the mandrel and external atmospheric pressure. The mandrel is then rotated to wrap the plastic blank around the curved external surface of the mandrel. When a complete rotation is effected to overlap ends to form an open-ended tubular plastic sleeve. A preheated rigid base article such as a cylindrical container is positioned above the mandrel so that their longitudinal axes are coincidental. A stripper ring, also longitudinally aligned but positioned below the mandrel, is moved upwardly until it engages the plastic sleeve on the mandrel and pushes it telescopically upwardly onto the rigid base article or container. The heat retained in the article causes the plastic sleeve to shrink slightly such that it remains in position on the article after the stripper ring is lowered. The article with its plastic sleeve temporarily mounted thereon is then subjected to a final heat-shrinking process such as in a tunnel oven where the heat-shrinkable sleeve is contracted to tightly conform to the underlying article surface.